We instituted the new magic item purchase restrictions in my last session of Felltower.
How did it go?
A few things happened:
Significantly Less Purchases
Because special ordering magic items, especially buffing items and casting items, isn't really an automatic process, the amount dropped off significantly. It went from a series of emails of "How much is this? How about this? What if it does X instead of Y and only 2*Z instead of 3*Z?" to "I'm ordering some custom cloth armor, I'll give you the math on Sunday" and "I'm getting one of those Puissance +1 weapons I've been needing."
So for me, that was a big win. Less work calculating costs, times, remembering who ordered what, etc. etc.
More Potion and Consumable Purchases
On the other hand, people bought a lot more potions. Cleaning out the house on Great Healing Potions for example, and stocking up on some of everything else.
Alchemist's Fire and similar items also went well.
Normal items sold about the same, though, mostly because people don't need-need them.
More Basic Spending
At least one person overspent on upkeep in return for bonuses to rolls in town. Living it up means you get more attention, and that translates in all ways. This went from "only do this when I really need it" to "may as well do this because I expect to make some rolls that matter."
We also got more spending on finding hirelings - suddenly 400 for a crier to go out and announce your job posting didn't seem crazy. They went from "only the guys who are listing themselves on Craig's List" to "let's put out actually ad copy to find real candidates."
More Generosity to Hirelings
Not only did people spend more trying to find hirelings, but even on a costly and loot-free delve they gave out tips and paid what they owed.
Emergency Funds Were On Hand
Critical, this one. Because Hjalmarr didn't break the bank spending all but a few hundred on new magical everything he had the $24K on hand to pay his Resurrection donations. The Good God giveth, but the Good God demand you giveth to receiveth.* Had he ordered all the stuff he wanted, they'd have had to take up a collection to pay for this, and possibly sell just-purchased gear and hurriedly try to cancel orders like someone hitting the "Undo Send" button on Google.
This made me really happy - not the dying part, although that was funny and I didn't think the magic ring's False Aura was going to pass detection (hurrah for poor rolls). It was rather the "we have cash on hand after a big haul." I was really tired of dead-broke guys a session after a huge haul, and the only time anyone had cash on hand was when they got some, but not enough, money.
So all in all, I think the rule did what I wanted. I feel bad taking back something that was an option the whole game, but it wasn't working out. The above is really what I wanted - occasional special orders, the good stuff being in the dungeon, and PCs with cash on hand to spend in town on the things I expect people to buy.
So I think it's working. The party should be able - after a big haul - to repair lots of damage, undo disaster to a degree, replace gear, etc. It shouldn't be firesale time because everyone is in debt up to their ears for magical items needed to survive delves to get money to buy magic items to survive delves.
So far, so good.
* Do not the scriptures say, "Let the poor man be welcome into my kingdom in the afterlife, and let the rich man fork over $15K or so to finish his work upon the earth and then be welcome once he's poor?" Probably not, but it sums up to about that.